In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention.
Milling tools are provided for the gear milling of gear wheels in different modules Mn depending on the size of the gear wheels to be manufactured. There are modules from Mn=1 for very small gear wheels, to Mn=22 or more for very great gear wheels. The disclosed tool can be used for gear wheels of all modules but is particularly suitable for the milling of gear wheels with Mn=3 to Mn=8.
U.S. Pat. No. 5,593,254 shows a milling tool formed for the hobbing of workpieces having cogs, such as gear wheels, racks and the like. The milling tool comprises a tool body that defines a rotation axis and should have a fixing end, an opposite outer end, and a peripheral surface that extends around the rotation axis between the fixing end and the outer end. The tool body comprises a large number of seats that are arranged one after the other. In each seat, a milling insert is arranged. The milling insert has an upper side that forms a chip surface, an under side and two opposite, converging main cutting edges. The main cutting edges are connected by a front transverse end cutting edge. The milling insert is fastened by a screw that extends through an eccentric hole of the milling insert from the upper side to the under side. The milling insert has a ridge on the under side that is in engagement with a groove in the seat. The upper side of the milling insert forms a chip surface that leans in relation to a radial plane in respect of the rotation axis. This causes an error of the involute of the cogs that are to be milled.
EP-A-2 072 162 shows a milling tool formed for the hobbing of a workpiece having cogs, such as gear wheels, racks and the like. The milling tool comprises a tool body that defines a rotation axis and has a fixing end, an opposite outer end, and a peripheral surface that extends around the rotation axis between the fixing end and the outer end. Furthermore, the tool body comprises a number of seats that are arranged at the peripheral surface one after the other along a helix line having a constant pitch. The milling tool also comprises a corresponding number of milling inserts. Each seat is formed with a support surface that supports a milling insert projecting from the tool body. Each milling insert comprises a row of three teeth. Each tooth is formed for engagement with a gash of the workpiece. Each milling insert has an upper side that forms a chip surface for each tooth. The chip surfaces of the three teeth are lying in a common plane, which means that a normal of the chip surface will form an acute angle with a tangent of the helix line where this intersects the chip surface at least for two ones of the teeth.
JP-A-2001-353621 shows an additional example of a milling tool for hobbing. The milling inserts are formed with a row of teeth. The individual teeth of the milling tool are arranged along a helix line. Each tooth is formed for engagement with a gash of the workpiece. The milling inserts have an upper side that forms a chip surface having a normal that forms an acute angle with the tangent of the helix line. As in the milling tool that is shown in U.S. Pat. No. 5,593,254, the chip surfaces lean in relation to a radial plane in respect of the rotation axis.
U.S. Pat. No. 5,593,254, EP-A-2 072 162 and JP-A-2001-353621 as well as the present disclosure relate to a milling tool wherein the seats of the milling inserts extend essentially radially. There are also milling tools for hobbing wherein the seats of the milling inserts extend essentially tangentially. An example of such a tool having tangential seats is shown in U.S. Pat. No. 4,218,159. This type of milling tool has the disadvantage that it requires at least twice as many milling inserts, two for each gash. By milling tools having radial seats, each milling insert can be formed with a pair of main cutting edges that simultaneously are in engagement with both cogs that surround a gash.